Photographic silver halide emulsions containing a ruthenium, palladium or platinum hydroxide in stabilizing amounts and process for preparing the same



United States Patent O AMOUNTS AND PROCESS FOR PREPARING- THESAME VereMallet, Milltown, N.J., assignor to E. I. du Pont de Nemours andCompany, Wilmington, Del., 2 corporation of Delaware No Drawing. Filed'Aug. '28, 1957, s... No. 680,648 9 Claims. c1. 96-110) This inventionrelates to photographic silver halide emulsions of improved stabilityand to a process of preparing the same. More particularly, it relates tosuch emulsions which contain water-insoluble hydroxides of ruthenium,palladium or platinum, and to a process of preparing the same.

Many compounds are known which have a good stabilizing or antifoggingaction in photographic silver halide emulsions. The utility of many ofthese compounds, however, is severely limited by their tendency todecrease the sensitivity of dispersions of light-sensitive silver halidein water-permeable colloids. Moreover, since the amount of the knownstabilizing agents which can be added to a silver halide dispersion oremulsion without producing deleterious eifects must be kept within avery narrow range of exceedingly low quantities, it is difiicult tocontrol the quality of the dispersions from batch to batch.

An object of this invention is to provide photographic silver halideemulsions of uniform quality and enhanced stability to aging,particularly with respect to aging under conditions of relatively highhumidity and at elevated temperatures, e.g., tropical conditions.Another object is to provide such emulsions which are opticallysensitized. A further object is to provide a process for increasing thestability of photographic silver halide emulsions, especially high-speedsilver iodobromide emulsions, optically sensitized and not, withoutadversely affecting the sensitivity of the freshly prepared or coatedemulsions. A still further object is to provide such a process whilesimultaneously reducing the degree of fog produced upon aging andwithout adversely affecting the sensitivity of the aged emulsion layersof photographic films and papers. A still further object is to providesuch process wherein the amount of stabilizing agent added does not haveto be maintained within a narrow range. Still further objects will beapparent from the following description of the invention.

The foregoing objects are attained and stable photographic silver halideemulsions and emulsion layers provided in accordance with the inventionby adding to an aqueous light-sensitive silver halide emulsion a smallamount of at least one water-insoluble metal hydroxide of a metal takenfrom the group consisting of ruthenium, palladium and platinum, whereinthese metals have their principal valencies.

The above metal hydroxides preferably are added to the emulsion afterthe completion of the digestion stage where the emulsion is brought toits optimum sensitivity prior to coating. Various emulsion adjuvants canbe added to the digested emulsion, prior to, simultaneously with, oreven subsequent to the addition of the water-insoluble heavy metalhydroxide. Among such adjuvants are spreading agents, anti-foamingagents, sulfur sensitizcrs, e.g., sodium thiosulfate, thiourea, allylthiourea and allyl thiocarbamide, and sensitizing amounts ofpolyoxyalkylene compounds containing at least six oxyalkylene groups of2 to 3 carbon atoms.

grams of glass beads.

'ice

The emulsion sensitizing agents of the polyoxyalkylene type can bepresent in the emulsions in the usual sensitizing amounts. The usefulagents of this type include (a) various polyoxyalkylene glycols andderivatives thereof, e.g., alkyl ethers, fatty acid esters and (b)condensation products of hexitol ring dehydration products with ethyleneoxide or propylene oxide containing at least six oxyalkylene groups,having a molecular weight, or an average molecular weight of at least400 to about 8000 or more. Suitable compounds of these types aredisclosed in US. Patents 2,423,549, 2,441,389, 2,240,472, 1,970578 and2,400,532.

In preparing the stabilized emulsions of the invention, thewater-insoluble heavy metal hydroxide is used in very fine particlesize, e.g., from 2 to 50 and preferably 2 to 10 microns, and ispreferably added from aqueous dispersion. The dispersion or suspensioncan be easily prepared from the pure metal hydroxide.

As an exemplary procedure, a suspension of these materials is preparedby first weighing out 5.0 grams of the metal hydroxide and adding tothis amount about 20 To this mixture there is added 20 ml. of distilledWater. The mixture is placedin a ball mill and mixed for 48 hours. Theglass beads are then removed and the suspension diluted with distilledwater to a convenient concentration, usually about .01 gram of the metalhydroxide per 1000 ml. of distilled water. The procedure for preparationis the same for each of the metal hydroxides.

The optimum amount of the metal hydroxide stabilizer may vary for agiven emulsion depending on the presence of emulsion adjuvants such aschemical sensitizcrs, optical sensitizcrs, etc. We have found that theamount to be added should be less than 0.1 mole of the metal hydroxideper 1000 moles of silver halide. The preferred ranges are 0.0095 to 0.95mole of palladium hy- .droxideand 0.0087 to 0.087 mole of rutheniumhydroxide per 1000 moles of silver halide.

In the case of platinum hydroxide, it preferably should be kept below0.0063 mole and above 0.0025 mole per 1000 moles of silver halide.

The invention is useful in stabilizing various types of silver halideemulsions including silver chloride, silver bromide, silverchlorobromide and silver chloroiodobromide emulsions of pH 5.0 to 8.0and greater, and

agents are natural and synthetic colloids, e.g., albumin,

casein, agar-agar and polyvinyl alcohol and its partial ethers, estersand acetals.

The following examples will further illustrate but are not intended tolimit this invention and in the tables the amount of metal hydroxide isin parts of grams or grams per mole of silver halide, which is referredto as AgX. In these examples, the emulsions are prepared and coated inthe absence of actinic radiations in amounts which would cause asignificant exposure of the emulsions.

Example I A high-speed gelatino-silver iodobromide emulsion of the X-raytype containing approximately 1.5 mole percent silver iodide and 98.5mole percent silver bromide is prepared in the conventional manner. Theemulsion is divided into two equal parts which are given a normaldigestion. One digested part, without further treatment, is coated ontoa cellulose acetate film base. To the other part, palladium hydroxide,Pd(OH) in the amount shown in the following table, is added. Samples ofthe filmelements were then given an X-ray screen exposure of 15'milliampere-seconds, 71 kilovolts potential, at a distance of 55 inchesthrough a 1 millimeter aluminum filter using an aluminum step wedge andthen were developed in a developer of the following composition:

Grams N-methyl p-aminophenol hydrosulfate 3.0 Hydroquinone 9.0 Sodiumsulfite (desiccated) 50.0 Potassium bromide 4.5 Potassium carbonate 50.0

Add water to make 1.0 filter.

for 5 minutes at 68 F. with the results shown in the following table:

7 days-120 F.-65% RE. Fresh Pd(H)g Speed 0011- Fog trast Speed Con- Fogtrast None 1,000 3.24. .03 990 2.30 .11 0.0133 1,060 3.27 .03 990 2.40.07

Example 11 Example I is repeated except that the emulsion .is di videdinto four parts which are digested, and ruthenium hydroxide, Ru(OH) isadded in the amounts shown in the following table to three parts inplace of the palladium hydroxide. The film elements were exposed anddeveloped as described in Example I with the results listed in thefollowing table:

7 days-120 F.65% R.H. Fresh Ru(0H) Speed Con- Fog trast Speed Con- Fogtrast Example Ill Example I is repeated except that the emulsion isdivided into four parts which are digested and platinum hydroxide,Pt(OH) -2H O, in the amount shown in the following table, is added tothree parts in place of the palladium hydroxide. The film elements wereexposed and developed as described in Example I with the results listedin the following table:

Example I is repeated except the emulsion is divided into four equalparts and Pd(OH) in the amounts shown in the following table, is addedto three portions in lieu of the amounts indicated in Example .I. Thefilm 4 elements were exposed and developed as described in Example Iwith the results listed in the following table:

7 days-120 F.-65% R.H. Fresh Pd(OH)z Speed Con- Fog trast Speed .Con-Fog trast and complexes have been of the water-soluble type. Palladiumchloride and nitrate, for example, when used in stabilizing amounts,desensitize a silver halide emulsion. Platinum complexes have adesensitizing effect on silver halide emulsions. Platinum chloride hasno appreciable effect as a sensitizer.

An advantage of the invention resides in the fact that the metalhydroxides used, being insoluble, do not have a localized reaction atthe point where the stabilizer is introduced into the emulsion. Ions arereleased more slowly, and this leads to more uniformly stabilizedemulsions than it has been possible to obtain by means of water-solublemetal compounds.

An advantage of this invention is that it provides a simple andeffective process for improving the stability of photographic emulsions.The process is not only simple but it uses chemical compounds which areeasily prepared. Another advantage is that the process of stabilizingthe emulsions can be practiced successfully by the ordinary technician,and extreme care does not have to be exercised in the amount of metalhydroxide added since a relatively large amount still contributesstabiliz- -ing properties to the emulsion. Stabilization of the fresh-1y prepared and coated emulsions, moreover, is accomplished withoutadverse effects on the optimum sensitivity of the freshly preparedemulsions. The emulsions have high initial speed and good stability,that is, have relatively low fog values initially and upon aging.

I claim:

1. A process for the stabilization of a digested photographicwater-permeable colloid-silver halide emulsion which comprises uniformlyadmixing with said emulsion an aqeuous dispersion of finely dividedparticles of a water-insoluble metal hydroxide taken from the groupconsisting of ruthenium, palladium and platinum hydroxide in astabilizing amount less than 0.1 mole per 1000 moles of silver halide.

2. A process as set forth in claim 1 wherein said colloid is gelatin.

3. A process as set forth in claim 1 wherein said hydroxide has aparticle size of not more than 50 microns in average diameter.

4. A process as set forth in claim 1 wherein said emulsion is ahigh-speed silver iodobromide emulsion.

5. A water-permeable colloid silver halide photographic emulsion havinguniformly admixed therethrough a stabilizing amount of at least onewater-insoluble metal hydroxide taken from the group consisting ofruthenium, palladium and platinum hydroxide which is present in anamount above 0.0025 and less than 0.1 mole per 1000 moles of silverhalide.

6. A photographic emulsion as set forth in claim 5 wherein saidhydroxide is present in the form of particles having an average diameterless than 50 microns.

5 6 7. A photographic emulsion as set forth in claim 5 References Citedin the file of this patent wherein said colloid iS gelatin. UNITEDSTATES PATENTS 8. A photographic element comprising a sheet supportbearing at least one layer of a water-permeable colloid 2489 )3 41 wane?et a1 1949 silver halide photographic emulsion having uniformly 5 1 3Baldslefen 1951 admixed therethrough a stabilizing amount of at least2,7 33 Walk Sept- 1955 one water-insoluble metal hydroxide taken fromthe group consisting of ruthenium, palladium and platinum OTHERREFERENCFS hydroxide which is present in an amount above .0025Paftmgtolli Textbook of lnollgamc 'y P- and less than 0.1 mole per 1000moles of silver halide. 10 955, 5th Macmillan -s London- 9. An elementas set forth in claim 8 wherein said support is a hydrophobic film base.

1. A PROCESS FOR THE STABILIZATION OF A DIGESTED PHOTOGRAHICWATER-PERMEABLE COLLOID-SILVER HALIDE EMULSION WHICH COMPRISES UNIFORMLYADMIXING WITH SAID EMULSION AN AQEUOUS DISPERSION OF FINELY DIVIDEDPARTICLES OF A WATER-INSOLUBLE METAL HYDROXIDE TAKEN FROM THE GROUPCONSISTING OF RUTHENIUM, PALLADIUM AND PLATINUM HYDROXIDE IN ASTABILIZING AMOUNT LESS THAN 0.1 MOLE PER 1000 MOLES OF SILVER HALIDE.